In present day color photography the effect of color is obtained by three or more emulsions that are superimposed on a base with optical filters between the layers of emulsions. The base may be a transparent one such as a sheet of cellulose acetate, or it may be an opaque one such as a sheet of paper. Additional layers may be present such as antihalation layers, etc. Essentially the color is found in, generally, three separate emulsion layers. Each of the unexposed layers contains a light sensitive silver salt or silver halide and some form of coloring material that is originally substantially colorless but which during the processing of the film is converted to a color in proportion to the amount of silver in the silver image.
The nature of the photographic process is such that a color image can not be any sharper than the original silver image which it replaces and very often the color image loses a certain amount of detail or resolution. Because of the nature of the color process itself, it is difficult to increase the resolution of the color images, but it has been found possible to increase the resolution of the overall image by making use of a thin silver image in conjunction with the color image.